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VVR2.pdf


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While it is a simple circuit it is not a simple mod to install. It should only be installed by
a qualified amplifier technician. Use this circuit at your own risk! I do not warranty it,
either expressed or implied, for any use in any amplifier. By installing this board in
your amplifier, you are agreeing that you will assume all responsibility for its safe
operation. If you don’t agree with these terms then send the board back in re-sellable
condition for a full refund.
The VVR board is designed to be used on amps of 50 watts and lower. I am sure that by
adding an additional (paralleled) mosfet and a few more components it could be made to
work with higher power amps. Between 30 – 50 watts heat becomes an issue and you
need to add some kind of heat sink for the mosfet in addition to just the amp chassis.
Aluminum dissipates heat better than steel. I have successfully used the VVR in amps
from 5 to 30 watts without needing to add additional heat sinking other than the chassis it
self. With the mosfet bolted to the chassis it should just get warm and not hot to the
touch. You should test for proper heat sinking after installation at different power levels
and after different periods of playing time.
You can regulate voltages to just your power tubes or the whole amp or any other portion
in between. You need to talk this over with your tech as there may need to be additional
parts that need to be installed in addition to the VVR board. It would be impossible for
me to offer design assistance to install this in any amplifier that has ever been made. In
the following pages, I will try and give you as much info as I have available. The board
can be used for either fixed bias or cathode biased amps. Some parts are omitted from the
board if you are installing it in a cathode biased amp. See BOMs below

Bill of Materials for fixed bias is
1)
1)
4)
1)
1)
1)
1)
1)

dual 1 meg pot 1/2 watt Linear
1meg trim pot 1/2 watt
100k 1/2 watt resistors (R1, R2, R3, R5)
10 ohm 5w resistor (R4)
12v zener 1w (ZD1)
12v zener 1w (ZD2)
NTE2973 (or equivalent) Mosfet (Q1)
NTE2372 (or equivalent) Mosfet (Q2)

Bill of Materials for the cathode bias is
1)
2)
1)
1)
1)

single 1 meg pot 1/2 watt linear
100k 1/2 watt resistors (R1, R2)
10 ohm 5w resistor (R4)
12v zener 1w (ZD1)
NTE2973 (or equivalent) Mosfet (Q1)

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